Grunion science

•Grunion are 6-inch fish that live and spawn exclusively in Southern California and the northwest coast of Mexico, but their unique reproductive patterns most intrigue Californians and visitors alike.

•The grunion is the only fish known to spawn on land. They do so by washing on to the beach with the high tide during the full and new moons between March and August, with the peak in April and May.

•The females bury themselves in the sand up to their pectoral fins just below the high tide line. As she releases her eggs, as many as eight males then wrap their bodies around, releasing their milt, which trickles down her body and inseminates the eggs in the sand. The adult fish then wash back to sea.

•At the next moon cycle, the high tide causes the grunion hatchlings to wash into the sea as the adults repeat the mating ritual.

•The lives of grunion outside their reproductive cycle – such as how far from the coast they live and in what settings – are little known to scientists.

Rules for grunion hunting

If you decide to go out grunion hunting, remember a few key rules:

•You can harvest the fish only by hand.

•If you are 16 or older, you must have an active fishing license.

•You cannot hunt in April and May, which is the closed season.

SEAL BEACH – The moon was nearly full at the Seal Beach pier one recent night, and the grunion were running.

Except, they weren't, at least not really.

The moment one of the 6-inch-long, glimmering silver fish washed ashore, several grunion hunters would pounce on it, grasping and grabbling at the wet sand to scoop up the uniquely Southern California fish, which spawns on shore as part of its mating cycle.

Shouting with glee, flashlights brightly illuminating swathes of beach, the grunion hunters would race back to their plastic buckets to dump their prizes. Some buckets had upwards of 20 grunions, others just a handful.

But the hunting behavior – the searching, probing lights, the loud noises, the gaggles of people – were exactly the sorts of deterrents that keep the grunion from spawning in greater numbers, that prevent them from washing ashore by the hundreds and thousands in a shimmering, glimmering tide that no one at Seal Beach saw that night.

"You'll have people go and they catch them, and if they do that it tends to make the run a lot smaller because it scares the fish away," said Karen Martin, a Biology professor at Pepperdine University and the foremost grunion expert. "It can stop the run from happening."

The jury is still out on the exact mechanism of the grunion run, but scientists think grunion scouts wash ashore first, in essence surveying the beach. The other grunion in the water then can know from the scouts if a particular beach is suitable for spawning.

What's better known is what happens after the grunion wash ashore: Somewhere just below the high tide line, the females bury themselves tail-first in the sand, laying their eggs. Multiple males wrap their bodies around the females, releasing milt, which trickles down the females' bodies to inseminate the eggs. The fish aren't monogamous: the male may inseminate the eggs of many females on a given night.

Then, the adult fish wash back into the ocean.

At the next high tide on either a full moon or a new moon, the grunion hatchlings half the size of a BB wash back into the ocean. The adults spawn again, potentially many times over the course of a season, which lasts from March through August.

Other animals rely on the grunion as a valuable food source: herons and terns stand sentinel on the beach, waiting to swallow the small fish. But humans can easily decimate a grunion run – even a large run of thousands of fish – if they scoop them up in large enough numbers. Some people fry the grunions and eat them, some release them back into the ocean and some even use them as bait to catch fish, especially herring.

To protect the grunion, Martin partnered with California State Parks and other groups to change practices that harm the grunion. For instance, many beaches across Orange County now don't groom or rake below the high tide line during grunion season to make sure grunion eggs laid there aren't disturbed.

Martin also started the Grunion Greeter project in 2002, a citizen Science program that recruited volunteers to survey beaches known for their grunion runs and estimate how many fish are spawning, rating the runs on a five-point scale. Volunteers were trained, rewarded for reporting results and organized on a precise schedule. The surveys helped scientists know better when and where the grunion run.

But the program has fallen on hard times. Funding has dried up and though a few volunteers still report back with data, the network is much looser and not quite as organized.

The partnerships and the protective practices, however, remain. For example, Martin works closely with the Crystal Cove Alliance, which seeks to protect the ecosystems of Crystal Cove State Park. Harry Helling, president of the alliance, is an emissary for the grunion and beach health generally. Grunions, because they're so iconic, can serve as ambassadors for beach health to the public.

Related Links

Billy Le, 26, of Garden Grove uses a headlamp to help him spot grunion at Seal Beach on Wednesday evening. MACKENZIE REISS, ORANGE COUNTY REGISTER
Fisherman walk up and down Seal Beach on Wednesday evening, using only the light from their headlamps to spot grunion. MACKENZIE REISS, ORANGE COUNTY REGISTER
Quoc Tran, 30, of Westminster, displays a handful of grunions that he caught around midnight on Wednesday. During their mating season, grunion swim onto the shore, making them an easy catch for birds and fisherman alike. MACKENZIE REISS, ORANGE COUNTY REGISTER
Marine biologist Julianne Steers, one of the prominent grunion scientists in the region, spent an evening looking for the sometime elusive grunion. ROSE PALMISANO, ORANGE COUNTY REGISTER
Seen through a night-vision lens, Seal Beach is crowded at midnight on Wednesday as fisherman and casual observers walk along the shoreline in hopes of spotting grunion. MACKENZIE REISS, ORANGE COUNTY REGISTER
Quoc Tran, 30, of Westminster, displays a handful of grunion that he caught around midnight on Wednesday. During their mating season, grunion swim onto the shore, making them an easy catch for birds and fisherman alike. MACKENZIE REISS, ORANGE COUNTY REGISTER
Arthur Sargent, left, Michael Mihara and Spencer Sargent were disappointed not to find grunion lining the shore at Doheny State Beach on a recent night. ROSE PALMISANO, ORANGE COUNTY REGISTER
Brittany Tran, 16, of Buena Park places a grunion in a plastic bucket, along with the rest of her family's catch from Wednesday evening. Some fisherman throw the grunion back after catching them, while others prefer to batter and fry them. MACKENZIE REISS, ORANGE COUNTY REGISTER
Grunion swim onto shore to mate during full and new moons from March until August. MACKENZIE REISS, ORANGE COUNTY REGISTER
Billy Le, 26, of Garden Grove, and Paul Luong, 25, of Orange wade into the water in hopes of catching grunion fish as they make their way to shore at Seal Beach. MACKENZIE REISS, ORANGE COUNTY REGISTER

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